During intense exercise, skeletal muscle cells switch from aerobic respiration to lactate fermentation. Which of the following statements correctly explains why this metabolic shift results in a significantly reduced yield of ATP per glucose molecule?
The conversion of pyruvate to lactate is an endergonic reaction that directly hydrolyses two molecules of ATP per glucose molecule, reducing the net energy yield.
Glycolysis requires oxygen to actively transport the pyruvate produced across the outer mitochondrial membrane, meaning glycolysis cannot proceed efficiently in anaerobic conditions.
Without oxygen to act as the terminal electron acceptor, mitochondrial NAD+\text{NAD}^+NAD+ and FAD\text{FAD}FAD cannot be regenerated, halting the Link reaction and the Krebs cycle.
Lactate fermentation yields less ATP because the regeneration of oxidised NAD+\text{NAD}^+NAD+ occurs in the mitochondrial matrix, depleting the proton motive force.
